A carboxyl-containing polymer is used as a thickener for cosmetics and the like, a moisturizer of cataplasms and the like, an emulsifier, a suspension stabilizer of suspensions and the like, a gel base of batteries, and the like.
When the carboxyl-containing polymer is used for the above purposes, for example, the carboxyl-containing polymer is added to water or the like to prepare a homogenous dispersion, followed by neutralization by using an alkali, and the resultant is dissolved for use. However, since the carboxyl-containing polymer is generally fine powder, when the polymer is dispersed in water or the like, lumps (undissolved lumps) are easily formed. Once the undissolved lumps are generated, a gel-like layer is formed on the surface of the undissolved lump. Accordingly, the speed of water permeating to the inside of the undissolved lump becomes slow, which makes it difficult to obtain a homogenous dispersion.
In view of preventing the generation of undissolved lumps, for example, it is known that when an α,β-unsaturated carboxylic acid or the like is polymerized to produce a carboxyl-containing polymer, at least one of compound among polyol fatty acid esters and polyol fatty acid ester alkylene oxide adducts is added in a specific amount to perform polymerization, whereby a carboxyl-containing polymer composition showing excellent dispersibility in water is obtained (see Patent Literature 1).